Powder coating of articles provides advantages over other types of painting or coating. For safety reasons, and to collect excess particles which deflect off of articles during powder coating, powder coating typically occurs within a booth.
For relatively long articles such as extrusions, which may have a length of 20 to 30 feet, or even longer, it is advantageous to coat these articles while oriented vertically. In one approach to coating articles of this type, an overhead conveyor holds the articles in vertical orientation and conveys them in a horizontal direction through a powder booth which, in cross section, resembles a keyhole. In this approach, the powder booth must be at least as tall as the elongated articles.
During powder coating in a booth of this type, a substantial amount of powder sticks and accumulates to the inner walls. This powder must be cleaned from the inner walls of the booth when a particular job has been completed, or when the booth is changed over to coat with a different color. Because these keyhole shaped powder booths sometimes have a height as high as five (5) meters, it is necessary for a cleaning person to use a stepladder to clean the inner walls at the top of the booth. Using a stepladder, typical cleaning time for a booth of this type is about six hours. During this time, the powder booth cannot be operated.
In addition to this excessive downtime, cleaning efficiency is relatively low and risk to the operator is relatively high when cleaning is performed from a stepladder, due to the narrow dimensions of the booth. These factors result in cost increases in operating a powder coating booth for coating elongated articles.
As an alternative to a stepladder, a wheel supported crane, or "cherrypicker", could be used to elevate a cleaning person to the level necessary to clean the inner walls of a powder booth. However, such devices are expensive and difficult to maneuver within the confines of a typical manufacturing facility in which powder coating is performed.
It is an objective of this invention to simplify and to increase the safety level of cleaning the inner walls of a powder booth used to coat elongated articles.
It is another objective of this invention to reduce the costs associated with operating an apparatus for powder coating elongated articles.
It is still another objective of this invention to reduce the downtime normally associated with cleaning a powder coating apparatus.
The above-stated objectives are achieved via a powder coating booth equipped with an elevator which supports a horizontal platform within the booth and raises or lowers the platform to any desired elevation in the booth so that an operator standing on the platform can efficiently wipe clean the inner surface of the walls of the booth at any desired elevation.
According to one preferred embodiment of the invention, a powder coating apparatus includes a conveyor for conveying elongated articles along a coating line in vertical orientation, a pair of opposing walls which define the body of a powder booth centered on the coating line, powder spray nozzles extending through the walls and directed toward the coating line, and an elevator adapted to move a horizontal platform upward and downward to a desired elevation inside the booth. The platform is slightly undersized with respect to the distance between the walls of the powder booth, thereby enabling the platform to raise and lower without obstruction. The walls of the booth include opposing guide rails, and the platform includes horizontal slides which ride within the rails during vertical movement.
The elevator may include a hydraulic cylinder operatively connected to a pantograph linkage that supports the bottom of the platform. A number of other mechanisms may be used to raise and lower the platform, including a rack and pinion, a nut and bolt, a swinging arm, or any other suitable structure for vertically moving a horizontal platform. The particular application of the invention will dictate the preferable elevator structure for vertically moving the platform.
In operation, an overhead conveyor conveys the elongated articles along the coating line. The walls of the powder booth straddle the line. At a portion of the line dedicated to article coating i.e., a coating station, the spray gun nozzles extend through the walls of the powder booth and are directed inwardly toward the articles to spray powder thereon.
When excessive powder has accumulated on the inner walls of the powder booth, or when a job has been completed or the powder used in the coating operation is changed to a new color, the walls of the powder booth must be cleaned.
The location for cleaning depends upon the particular embodiment of the invention. If the powder booth and the platform/elevator are not horizontally movable, cleaning occurs at the same location as coating, but when the conveyor and coating line has been shut down. For this embodiment, the elevator may be recessed in the floor.
Several other embodiments of the invention utilize one or more cleaning stations laterally spaced away from the coating station and the coating line. The use of a spatially removed coating station in combination with a horizontally movable booth allows the coating line to operate almost continuously, or with reduced downtime needed for cleaning. For these embodiments, the spray guns are preferably mounted to brackets which are also horizontally movable. If desired, the platform and elevator may also be horizontally movable to the one or more cleaning stations.
Optimum efficiency for the coating line may be achieved with multiple movable powder booths, multiple coating stations, multiple cleaning stations, multiple stationary elevators, at least one horizontally movable elevator, or even with multiple coating lines, depending upon the circumstances.
The use of a vertically movable elevator within a powder booth reduces the time associated with cleaning a powder booth. Using the elevator, a wiping operation to clean the walls of the booth takes about two hours. The elevator also makes cleaning the walls of the booth a simpler and safer operation, compared to using a stepladder. Use of a cleaning elevator in conjunction with multiple powder booths reduces the downtime of a powder coating line used to coat elongated articles, thereby reducing the costs associated therewith.
These and other features of the invention will be more readily understood in view of the following detailed description and the drawings.